1. Field of the Invention
The present invention relates to cooling apparatus of the cold plate type and, more particularly, but not by way of limitation, to an improved cold plate having increased efficiency and drink dispensing capacity.
2. Description of the Related Art
Typical cold plates feature rectangular castings of a metal such as aluminum that surround tubes of another metal such as stainless steel. The casting transfers heat from fluids flowing within the tubes to ice residing on the top surface of the casting. Such cold plates normally reside in the bottom of an ice storage container with the ice storage container serving the dual purpose of absorbing heat from the fluids flowing through the cold plate and storing ice to be dispensed with the beverage. In the particular application of cooling and dispensing carbonated beverages, the tubes in the casting connect at their inlets to a carbonator, a water source, and a beverage syrup source to carry carbonated water, plain water, and the beverage syrup throughout the casting. The outlets of the tubes connect to mixing valves which dispense the carbonated water, plain water, and beverage syrup to produce the carbonated beverage drink.
Cold plates utilize the ice placed on their top surface as a heat sink which absorbs heat from the carbonated water, water, and syrup as they flow through the tubes within the castings. That heat transfer results in the ice changing phase (i.e., solid to liquid). Thus, the ice absorbs the heat as latent heat which means the overall temperature of the ice, when used as the heat sink, does not significantly increase. In that way, the heat capacity of the heat sink is greatly increased over what it would be if, for example, liquid water cooled to a freezing temperature were employed as the heat sink.
Although ice provides an efficient heat sink, the efficiency of the heat transfer process between the ice and cold plate limits the cooling imparted to the fluids flowing through the cold plate. Both the position of the tubes within the casting and the surface area of the top surface of the casting determine the efficiency of the heat transfer process. With respect to the surface area of the casting, a larger surface area transfers greater amounts of heat. However, beverage dispensers must occupy as little counterspace as possible; therefore, the top surface areas of the castings may not be enlarged sufficiently to produce a significant increase in the efficiency of the heat transfer process.
Alternatively, changes in the position of the tubes within their castings may be effected to produce a more efficient heat transfer process. That is, tubes located closer to the top surface of the casting will transfer more heat from the fluids to the ice than tubes located further from the top surface. Unfortunately, as shown in related art FIG. 1, the rectangular shapes of typical cold plates allow the tubes to migrate away from the top surface of the casting during the cold plate molding process. The molding of the tubes away from the top surface of the casting places a thicker layer of the casting between the tubes and any ice laid on the top surface of the casting. As a result, the heat transfer between the fluid flowing through the tubes and the ice over the top surface of the cold plate greatly diminishes. Accordingly, a cold plate that minimizes the distance between the tubes and the top surface of the casting is needed.